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2/16/2016 Tear Film Layers Basic Ocular Anatomy oil aqueous snot Lynn E. Lawrence, CMSgt (ret), CPOT, ABOC,COA Healthy Tears A complex mixture of proteins, mucins, and electrolytes coated by a lipid layer What functions does each layer of the tear perform? Lipid Secretion: Meibomian Glands Left: Transillumination of eyelid showing meibomian glands • Antimicrobial proteins • Growth factors & suppressors of inflammation Right: Secretion of lipid at lid margin • Soluble mucin helps stabilize tear film • Electrolytes for proper osmolarity (295-300) – pH slightly alkaline (7.4) • The lipid layer restricts evaporation to 5-10% of tear flow – Also helps lubricate Why is a tear salty tasting? Where does a contact lens rest? Lipid Secretion: Meibomian Glands A Healthy Tear Film What eye is this? 800 nm 8,000 nm 100 nm (WC Posey, Diseases of the Eye, 1902) Transillumination of meibomian glands How does the lipid layer aid in contact lens wear? A healthy tear film is comprised of 3 layers: Mucin, Aqueous, and Lipid (Transillumination image from Dry Eye and Ocular Surface Disorders, 2004) 1 2/16/2016 Two Primary Forms of Dry Eye Oil & Water Remember science class? Oil floats. Oil does not mix with water, but rather sits on top of water. Oil is what keeps water from evaporating. 800 nm 8,000 nm 100 nm The two primary forms of dry eye are Evaporative Dry Eye, also known as Meibomian Gland Dysfunction or MGD and Aqueous Dry Eye. The majority of dry eye sufferers have MGD. The Meibomian Glands The Tear Film Structure In Our Eyes The meibomian glands are located in the eyelids The aqueous (water) layer provides natureal lubrication and is produced by the lacrimal glands. The aqueous layer is protected by the lipid (oil) layer that is produced by the meibomian glands located in the eyelids. When your meibomian glands do not produce sufficient oil, water evaporates causing burning, redness, dryness, irritation and eye fatigue. This is called Meibomian Gland Dysfunction or MGD. Meibomian Glands & Blinking When we blink the meibomian glands express the necessary protective oils LipiView II: Interferometer Blockages in the meibomian glands result in insufficient oil to coat the tear film Blinking stimulates the meibomian glands to secrete oils and spread a protective oil layer across the tear film. When we partially blink the eyelids do not touch, so no pressure is applied at the meibomian glands to release these oils. Over time the oils harden in the glands and blockages develop. Avg LLT 35 nm Avg LLT 90 nm Avg LLT – Average Lipid Layer Thickness (LLT) in nanometers (nm). Number less than 90 indicates increased probability for MGD. 2 2/16/2016 LipiView II: Dynamic Meibomian Imaging LipiView II: Partial Blink Analysis A decrease in lipid layer thickness is associated with incomplete blinking. Increase in visual fatigue is associated with incomplete blinking. Meibomian gland structure is observed with Dynamic Meibomian Imaging (DMI). DMI produces three images (surface illumination, transillumination and merged) to capture a comprehensive view of meibomian gland structure. If left untreated, the glands can shrink and deteriorate. The loss of glands is unlikely to be reversible. Failure to treat blocked glands is likely to lead to further structural compromise. Surface Illumination Transillumination Merged (Surface + Transillumination) Presence of partial blinks greater than 40% of total blinks is considered contributory to dry eye condition. If partial blinking is present, patient education and blink training should be considered. Normal Gland Structure Gland Truncation & Dilation Severe Gland Drop Out Intervention & Prevention Meibomian Gland Evaluator Upper Eyelid Meibomian Glands Over Time Lower Eyelid Temporal Central Prevention Nasal Meibomian gland function is evaluated by assessing how glands respond to gentle force, imitating that of a deliberate blink. Intervention Current model of treatment is interventional. Future of MGD treatment must be preventative. NO OIL SECRETION (BLOCKED) No oil is expressed using the MGE CLEAR OIL SECRETION Glands are functioning using the MGE Anatomy OPAQUE SOLID SECRETION Glands not functional; requires more force than the MGE Blue Eyes • More Like to have: – – – – Melanoma AMD Photophobia Better with pain What function does the pupil have? http://www.msn.com/en-us/health/medical/7-things-your-eye-color-says-about-yourhealth/ar-BBiNSGg?li=AAa0dzB&ocid=IDMD&page=4&fullscreen=true#image=4 3 2/16/2016 The Eyelid • 7 Layers of the eyelids 1. Skin-thinnest layer 2. Subcutaneous connective tissue 3. Striated Muscle 4. Sub-muscular connective tissue 5. Tarsal plate or fibrous layer 6. Smooth muscle 7. Conjunctiva (Bulbar/Palpebral) Eyebrows and Eyelashes • Eyebrows – Thickened ridge of skin with short hairs – Diverts perspiration • Eyelashes – Also protects – Sebaceous glands at base of each lash are called Glands of Zeis which produce a lubricating fluid • Fluid can harden and clog the gland, producing a stye or painless chalazion. If painful and infected it is called an external hordeolum Cataracts (myotonia) are caused by? How are Hordoleum and Chalazions treated? Lacrimal Apparatus • Sometimes a person cannot produce natural tears that they might need some punctal plugs. Anatomy and Physiology of the Eyeball 3 Layers • Fibrous Layer *Cornea *Sclera • Vascular Layer *Choroid *Ciliary body *Iris • Nerve Layer *Retina *Macula *Optic nerve What are the three main parts of the crystalline lens? Sclera • White in color • Primary function is protection • Pierced posteriorly by the optic nerve • Acts as insertion points for the six EOMs • Junction between the cornea and sclera is called the Limbus What is the total power of the eye? What is the main function of each layer? Conjunctiva • An epithelial membrane which covers the anterior sclera and continues to the back surfaces of the lids to form a conjunctival sac • Has blood vessels which can burst and cause subconjunctival hemorrhage • Three parts – Bulbar – Palpebral – Fornix - where bulbar and palpebral meet Name the mucus producing cell? 4 2/16/2016 Cornea Cornea What is it called when blood vessels grow onto the cornea? • Composed of 5 layers – Epithelium…24 hr healing • • • • What happens when a patient gets a scar in the visual pathway? • • • • • Index of refraction is 1.37 Approximately .5mm in thickness Transparent Organ (no blood vessels / avascular) Primary function is refraction of light rays Refractive power approx + 45.00 D Outermost layer 5 cell layers thick Heals very quickly Does not scar – Bowman's membrane- layer just under the epithelium NOTE: will scar – Stroma – middle tissue that forms 90% of the cornea – Descemet's membrane- thin elastic layer deep in the cornea – Endothelium - only one cell layer thick; lines undersurface of the cornea, where it regulates corneal water content What is the crossover point for the nasal optic nerves? What cranial nerve is tied to corneal sensations? Endothelial detail with nuclei Confocal Scanner Aqueous Humor • • • Epithelial detail with nuclei • Manufactured by ciliary body Characteristics: – Clear – Watery consistency (99% H2O) Functions – Refraction of light – Intraocular Pressure (IOP) – Probably nourishes posterior surface of the cornea and the crystalline lens Flows from posterior chamber through the pupil into the anterior chamber Which cells do not regenerate Epithelium or Endothelium? How does aqueous flow out of anterior chamber? Crystalline Lens Crystalline Lens ...approx 12-14 diopters of power • 3 things happen during accommodation: – Pupils constrict – Eyes converge – Lens gets thicker • Functions – Refraction of light – Accommodation • The crystalline lens contains a high degree of protein • Focus adjustment of the eye • Presbyopia is the loss in accommodation – Changes in the lens protein causes the lens to lose its transparency which is a condition termed "cataract" – Aphakia is the absence of a lens. It can be removed during cataract extraction – First noticed around age 40. Due to a loss in flexibility of the lens Name the three main parts of the lens? How much focusing power does the lens have? 5 2/16/2016 Ciliary Body Iris • Most anterior portion of the vascular layer • Gives the eye its color, i.e. blue eyes, brown eyes, etc. • Consists of blood vessels, pigment and muscle tissue • Regulates light • Smaller with age • Located near the base of the iris and posterior to it • Composed of blood vessels and muscle fibers (ciliary muscle) • Cilliary process produces aqueous What does the sphincter muscle control? Ciliary body is attached to suspensatory ligaments called? Nerve Layer - Retina Vitreous Chamber • Functions: • Visual Receptors are Cones and Rods – Refraction of light – Internal support – Cones • Produce color vision • Give improved acuity • Used in day vision = “Photopic” = normal and high levels of illumination • Spots in vision may be floaters in the vitreous – Rods…120 million • Produce black and white vision • Function in dim light = “Scotopic” = low level of illumination – Cones and Rods… 6 million • Used under mesopic vision = between scotopic and photopic • Both rods and cones are used. Post vitreous detachment How many chambers are inside the eye? The _____ is the strongest refractive media and has about ____ diopters of power. The retina (Cranial Nerve II) Pigment epithelium Vitreous Which cranial nerve controls the superior oblique muscle? The levator palpebrae raises the eyelid and is innervated by CN #? 6 2/16/2016 Retina – 10 layers Outside of eye • • • • • • • • • • Identification of Retinal Layers NFL Pigment epithelium Rods Cones Outer plexiform layer Horizontal cells Bipolar cells Amacrine cells Inner plexiform layer Ganglion cells Nerve fiber layer ILM GCL IPL OPL Stratus OCT™ IS/OS NFL: Nerve Fiber Layer ILM: Inner Limiting Membrane GCL: Ganglion Cell Layer RPE/CC IS/OS: Junction of inner and outer photoreceptor segments RPE: Retinal Pigment Epithelium CC: Choriocapillaris Choroid IPL: Inner Plexiform Layer OPL: Outer Plexiform Cross-sectional image of live tissue; a virtual biopsy Vitreous (inside of eye) Nerve Layer - Retina • Optic nerve head (optic disc) – No receptors physiological blind spot – Point of exit of optic nerve – Appears yellow compared to the orange retina Nerve Layer - Retina • Ora Serrata – Land mark attachment site for choroid and retina – Most anterior portion of retina – Nearly all rods How many layers are in the retina? What is Pars Plana? Anatomy and Physiology of the extraocular muscles New Advancement • ARCUS II Retinal Prosthesis • Netherlands 2nd • Patient is Jerone Perk, has retinitis pigmentosa • Dr. Marco Mura, MD The Extra-ocular Muscles (EOM) Organized into an umbrella-like bundle among the orbital fat, orbital blood vessels and nerves Six muscles associated with eye movements Superior rectus (S.R.) Inferior rectus (I.R.) Medial rectus (M.R.) Lateral rectus (L.R.) Superior oblique (S.O.) Inferior oblique (I.O.) How many cranial nerves control these 6 muscles? 7 2/16/2016 Extra Ocular Muscles Extraocular Muscles • Medial Rectus - Most powerful, adduction, CN III • Inferior Rectus - Primary is depression, CN III • Lateral Rectus - Abduction, CN VI • Superior Rectus - Primary is elevation What is the name of the point where the muscles come together? Muscles and Function Which muscle close the eye lid and is innervated by cranial #7? Bony Orbit • Openings of the orbit – Purpose of openings • LR6…SO4…3 – – – – – – • Transmit arteries and/or veins to and from the orbit • Transmit nerves to and from the orbit Rectus Obliques Intorsion Extorsion Elevation Depression – Types of openings • Fissures (crevices/cracks) • Foramina (holes) – Major openings • Optic foramen - II cranial nerve - Optic Nerve • Supraorbital fissure - IV cranial nerve - Trochlear Nerve The transition zone between the sclera and the cornea is called? An obvious upward/superior deviation of the eye is called? Orbit 1. 2. 3. 4. 5. 6. Frontal bone…forehead Ethmoid bone…weakest Palatine bone…smallest Zygomatic bone…strongest Lacrimal bone Maxillary bone Cranial Nerves LR6SO4 3 Muscles • Lateral rectus muscles #6 …abducens nerve • Superior Oblique #4 …trochlear nerve • All other muscles are controlled by #3 … oculomotor nerve The conjunctiva has two divisions, they are? Name the 3 chambers of the internal eye? 8 2/16/2016 Anatomy Physiology • • • • • The Orbit Bones, etc. The Sinuses Locations Human Body Planes External Structures Eyelids Conjunctiva Eyelashes and Eyebrows Lacrimal System Visual Pathway Objectives • Define the visual pathway • Identify structures in the visual pathway • Testing used for the visual pathway • Identify defects within the visual pathway Anisometropia occurs when there is a _____________? The outer layer of the eyeball is called? Visual Pathway Visual Pathway • Visual pathway has seven structures • Physical • Physiological • Psychological – – – – – – – Retina Optic Nerve Optic Chiasm Optic Tract Lateral Geniculate Body (LGB) Optic Radiations Visual Cortex …where vision occurs What causes your physiological blind spot? Aniseikonia occurs when an object viewed by one eye is _________? Visual Pathway Retina • Divided into four quadrants like the brain • Fovea at exact center • Optic nerve head is located in nasal half • Each quadrant sees the exact opposite visual field Antimetropia occurs when __________ ? What is an exudate? What is papilledema? 9 2/16/2016 Optic Chiasm • Temporal fibers do not cross • Nasal fibers do cross • Some fibers from the macula cross while others do not What part of the brain does the vision occur? Growth beneath Pituitary Gland Visual Field Defects • Common types of field defects – Blind spots - Areas of blindness in the visual field – Hemianopsia - Blindness in one half of the visual field of one or both eyes • Homonymous - Involving the nasal half of the visual field of one eye and the temporal half of the visual field of the other eye • Incongruous - Homonymous heminopia Incongruous homonymous Binasal defect An area of blindness within a visual field is called? 10 2/16/2016 Is this possible? You be the judge Review Questions • The point where the upper and lower eyelids meet is called a. ora serrata b. canthus c. joint d. sphinx • The blockage of the meibomian gland is called the ___________ when it causes pain, and the _________ when it does not cause pain. Review Questions • The eyelid will protect your eyes from… a. blinking b. dust particles c. stray tears d. a burning punctum • What main muscles raises the eyelid? • Name the five layers of the cornea in order Review Questions Review Questions • The drain port for tears is called? a. canal of Schlemm b. punctum c. lacrimal gland d. zonnule of Zinn • In what layer of the eye will chronic diseases normally manifest? • What structure prevents a contact from going behind the globe of the eye? Review Questions • What are the layers of a tear film? • What is the most anterior part of the retina. • What is the total power of the Cornea, the crystalline lens assembly, and the overall eye? • What is the most posterior layer of the retina? • Where is tear mucin produced? • Why is the tear film important in contact lens wear? • The optic nerve is which cranial nerve? • What function does the Canal of Schlemm have? 11 2/16/2016 Review Review Questions • Opia means what? • Identify the name for the 3 parts of the conjunctiva • What is the difference between a tropia and a phoria? • In what layer of the eye will the retina be found? • Avascular means what? • What is the strongest bone of the bony orbit? • How many extra-ocular muscles are oblique? • What does the root word “papill” mean? • What muscle of the lid would be involved in ptosis? Review Questions Review Questions • _________ exist when the foveal lines of sight of the two eyes do not point at the same object. – – – – A. binocularity B. strabismus C. conjunctivitis D. FB sensation • Of the following all are anomalies of the binocular system except: – – – – A. strabismus B. Amblyopia C. anomalous correspondence D. conjunctivitis Review Questions • Which test checks for eye movement and helps detect the dominate eye? – – – – A. muscle H B. cover test C. visual acuity D. myopia • Glaucoma screening test that used puff of air onto the eye surface: – – – – A. NCT B. snellen C. amsler grid D. accommodation • When the power of the crystalline lens correspond with axial length of the eye, so that parallel light rays are appropriately refracted to focus on the retina is called? – – – – A. emmetropia B. ammetropia C. hyperopia D. myopia • An opacity of the crystalline lens is known as? – – – – A. photophobia B. cataract C. edema D. aphakia Review Questions • Which test uses Pseudo Isochromatic Plates? – A. IOP – B. color test – C. cover/uncover – D. snellen • This checks the power of the eye: – A. NCT – B. taking case history – C. Autorefractor – D. taking blood pressure 12 2/16/2016 Review Questions • Which test is used to check six cardinal position of gaze for motility? – – – – A. Muscle H B. APD C. Amsler Grid D. Tropia • Examination of the eye is performed by using a slit lamp or another name for slit lamp is: – – – – A. non-contact tonometer B. biomicroscope C. pupilometer D. lensometer Review Questions • What is a good tear BUT? • What device checks the brain-eye connection? • What device measures the distance between the pupils? • What device measures corneal thickness? 13